33Ah gel batteries questions

[biscuit]

Good afternoon. I do not understand my batteries. I put a pair of 33Ah gel batteries (Haze gel HZY-EV12-33) in my 50kg or so wheelchair earlier this year. I charge through the XLR, leaving the chair on charge at 27.6V all the time barring a couple of times a week when in use. But I do not understand the charging. When those batteries were new the chair would draw 10A for maybe up to a couple of minutes. At that time I guessed it was because of my usage, the voltage I set and the low capacity of the batteries. These days it draws maybe up to 2A and reduces to no current in a couple of hours, or so says the display on the PSU. Something has changed, and I don't think it is my usage of once or twice a week, occasionally more or less.

Does the chair draw a chunk of current at intervals to maintain 27.6V? Or, as it is a cheap unit, will really low current display on the PSU as 00.00A?

Is this low current and short time because I am scarcely challenging the batteries with my usage?

Is 27.6V good when it is cold weather?

[Burgerman]

I charge through the XLR, leaving the chair on charge at 27.6V all the time barring a couple of times a week when in use.

Will cook them, cause internal positive plate corrosion, and electrolyte drying out (gel shrinkage/voids).

27.6 is like 13.8V per battery.
13.8V is OK for CHARGING a battery and it willtake a full day to completely charge a discharged battery.
Overnight to top up a stored, or very lightly used battery. Its used for FLOAT charging where time isnt critical.

13.6V will still charge but takes twice as long to be full. Used to make sure that a battery is topped off when the charge stage ends. OK for anything up to 2 or 4 days. A week at a push.

13.3V is for STORAGE where you can leave it conected indefinitely to keep it as healthy as possible. It wont properly charge, that should be done first. Long term float is meant to keep a battery at 101% and not allow it to discharge but also not draw any significant current. So maybe a few mA after a week. A 50A power supply cant accurately read that low. But it doesent need to.

A XZD will work for this but its eating power and doing almost nothing if left running indefinitely Which is why I use this:
https://www.wheelchairdriver.com/board/ ... =2&t=12590

But I do not understand the charging. When those batteries were new the chair would draw 10A for maybe up to a couple of minutes. At that time I guessed it was because of my usage, the voltage I set and the low capacity of the batteries.

A charger/power supply doesent charge at any specific current. It simply pesents a voltage.
IF in simplistic numbers the battery is at 12V and the charger at 13.6V then thats a 1.6V difference.
So what happens? Power tries to go from the 13.6V to the 12V battery. But its not in much of a hurrey as the difference is just 1.6V in this example.
So what determines this current level? RESISTANCE of the cables and connectors. And of the battery itself. If these were all 0 ohms, then it will pull as many amps as the charger can supply.
Of this resistance is high, infinitely high, zero current will flow.

This is why a low resistance (ow impedance) battery, and heavy cables and maybe an anderson connector is important! It speeds up battery charging as it pulls more amps.

These days it draws maybe up to 2A and reduces to no current in a couple of hours, or so says the display on the PSU. Something has changed, and I don't think it is my usage of once or twice a week, occasionally more or less.

So what changed in your case? You probably have an increased battery resistance as you kept them on float at too high float voltage indefinitely... So now low current flows.

Does the chair draw a chunk of current at intervals to maintain 27.6V? Or, as it is a cheap unit, will really low current display on the PSU as 00.00A?

Is this low current and short time because I am scarcely challenging the batteries with my usage?

Is 27.6V good when it is cold weather?

What temp re he batteries?
Thats too high for 90% of the time.
Set 13.3 to 13.35V for long term float.

[biscuit]

thank you.

[ex-Gooserider]

It is possible that having charged the batteries at the higher voltage and left them on it for so long, that you have fried them to a significant degree... What is your range like? If it gets you through your use then not a big deal, if not you may be in for needing a new set that you can charge at the right voltage as BM suggested...

ex-Gooserider

[Burgerman]

True. But also its possible to increase the IR and not lose significant range too. So if the chair has low demand, mild programming, it may still perform OK in that situation. It just cant make significant current or be charged as fast as before.

Odyssey charge much faster than MK gel do for e.g. Because they charge at 14.7V (bigger difference between full batt voltage and charge voltage) and because they have half the Int Resistance. You can get 90% charge from 0% on an odyssey with a powerful charger in 1 hour. That last 10% still takes 8 hours...

[biscuit]

I don't leave it on 27.6V all the time, I use the chair once or twice a week to do errands. And if I don't do errands I reduce the PSU output to 26.7V when I should have gone out.

When I get home after errands by chair I have a full row of battery indicator lights. The chair has had a sluggish feeling ever since I installed those batteries, more so than the AGMs. I try to ignore the sluggishness.

Fortunately I can relatively easily change this size batteries (the right dimensions for my chair) when they die and these batteries are fine for driving still, though reluctant to take a charge. Perhaps they are congenitally high resistance.

The thing is my battery usage isn't really a deep cycle, is it? Not many Ah used and very many hours between cycles.

[Burgerman]

When I get home after errands by chair I have a full row of battery indicator lights. The chair has had a sluggish feeling ever since I installed those batteries, more so than the AGMs. I try to ignore the sluggishness.

Slugishness is what I feel when I use crappy batteries. And even MKs compared to the Odyssey. I hae a set of haze EV 80Ah batts and they are as good as the MK or better.

A 33Ah batt though is automatically going to be double the IR and half the current capability of a 60Ah or 80Ah battery.

And if its starting out at a disadvantage then its quite likely it is high resistance you feel. Or has ended up that way.

Try a 14.1V charge, for 8 to 12H at CV. Not more.
Even a single charge at 28.8V as continually charging at 27.6V isnt really enough in cyclic use.

FORGET about joystick battery lights. Those are meaningless. And a full set of lights tells you that its anywhere from 70% charged upwards. And if you have half the lights out it can still be 95% charged but voltage depressed because of surface charge or high resistance.

You might even have a bad cell or something.
If it were me I would measure impedance, compare to each other and to spec. And I would measure battery voltage under load individuelly and while at reast and while on charge. Both batts should be practically identical. And 8 hours after charge be sat around 13.05V each.

[biscuit]

My PSU can do 0 - 10A and I have it at 10A, but my chair seems to draw about 2A. It could draw more for a few cycles when first installed, or so the PSU display said. Even 10A, then reduced every cycle. I mean the initial current, which drops to 0V on its own. Should I be reducing the initial current when charging?

I shall test the voltage (and the resistance if my multimeter can do it), then equalise the pair and tomorrow during the day I'll run the cycle you suggest.
Thank you.

[Burgerman]

Your battery may only draw 2A as its not discharged much. Run it low!
That will test range, and resistance if it draws high amps recharging.

You need a 4 wire tool to measure impedance as an AC frequency. These probes each have two wires and "points".Zoom into the black one and you can just about see this. It Injects AC and measure impedance at 1000hz directly at the terminal so it isnt measuring the test leads! Cheap from china. You cant do it any other way unfortunately. You can measure the other things as I said above though.

This shows the 0.22 of a mOhm on my LiFePO4 call.
So 8 of these, (for 24V) is 0.22mOhm x 8, only 1.7mOhm total!
https://www.aliexpress.com/item/32999842460.html

[biscuit]

I didn't do half the tests you recommended. I did measure the voltage of each battery and found 00.01V difference between the two, accumulated since I equalised them before installing in May. The terminals were securely bolted. My charge lead seems to be pretty thin wire, AWG 12 or so at a guess, I think it's an early one I chopped off a 2A charger once. Idk what that is in mm.

Now sitting connected in parallel until I put them back in the chair and charge them at 28.2V.

[Burgerman]

What is the voltage at?

Get a load of somekind. A car headlamp bulb or something.
Connect them in parallel as you have and use it to discharge them down to APROX 10.8 to 11.2 ish Volts.

Then charge. At 14.1V or 28.2V until the current stops falling by around 1/10th of an amp per hour. That will be about 8 to 10 hours at CV voltage. It will charge at high amps.

It will also maybe rejuvanate them.

[LROBBINS]

awg12 is good for 20A in an in-wall cable, more in open air.

[Burgerman]

I think she is mistaken with the 12 part.

I use that at 40A silicone with the PL8!

[biscuit]

It's 12 or maybe 14 awg.

I use that at 40A silicone with the PL8!

I on the other hand chopped my lead off a cheap charger many years ago and soldered a pair of banana plugs on.

I will see what I can find for a load. Might need to apply to the neighbours.

Can I use the PL8 to discharge and then charge? It will be convenient. The PL8 charging will time out at 8 hours +CC time. It will make a graph for me. When the charge amp line starts to look horizontal I stop charging?

[Burgerman]

Ys, set the PL8 to discharge it to 10.8V (1.8v per cell).

When the charge line is horizontal that is the time you must wait as the current drops away. While its at 14.1V per battery. That horizontal part needs to be 8 hours long if deeply discharged.

Set the PL8 to stop charge at 1000thC (2 IN PARALLEL is 66Ah) so set termination current to say 70mA or 8 hours whatever occurs first.

[Burgerman]

Voltage climbs first stage, at whatever max current you set.

Voltage then held steady at 14.1V or whatever you set while current falls away.

[Burgerman]

Heres one thats not finished yet...

[biscuit]

I've never used the PL8's discharge function. IIRC (and I should, as I've seen it often enough, but I instantly forget any numbers that aren't actually in front of my eyes) the PL8's discharge current will be something below 4A. I think the PL8 prompts me for a discharge current value and I would kind of prefer it to be <10A like my cheap PSU is. How long can I expect it to take, or what are the termination criteria, please?

[Burgerman]

Its 100 Watts max.
When DISCHARGING the PL8 takes almost no power from the power supply. It turns the battery energy into warm air and blows it out of the rear!

Since that means that it cant do more than 100 watts discharge, then you can set Amps to anything you want... It will never be able to exceed 100 watts.

During discharge from say 13V initially to 11 ish volts eventually thats a nominal 12V. So 100w div by 12V is what? 8.3A? Half of that for 24V as its maximum.

Now if you just want to cycle it, so you can improve it, or see it charge at high amps again, dont much care about accurate capacity measurement, just set it to 10A discharge. And thats the max it can do. You will never see that 10A. But it can only do that 10A on a lower voltage liKe a single lithium cell or a 2 cell pack like my camera.

***********************
If you want to do an ACCURATE capacity test then you need to do the following:
Discharge the battery, each one individually, over 20 hours Or rather the 20h rate. Why? Because your battery is rated at a 20 hour discharge capacity. Do it slower and get more than your 33Ah. do it faster and you will get less. This is due to the surface charge effect.

So you would set these settings:
CHARGE FULLY FIRST, at 14.1V for 8 hours at CV.
Divide the 33Ah (33,000mAh) by that 20hours. So thats 1650mA. Or 1.6A discharge.
After APPROX 20 hours if its healthy it will reach the 10.2V point you will need to set. That will give a FULL 100% discharge and you will be able to read off the actual capacity in mAh.

Like this, test on a 24V setup and an 76Ah AGM battery.
It is ALMOST finished here. And reading about 75,000mAh (75Ah).

But you must be exact, at 20 to 25 centigrade, charge properly first, etc.

[biscuit]

Oopsie, I can't continue today! I have errands, I had forgotten. So I have to close up and continue this test on Monday.

I will have some help then, too. It's not a one-girl job to remove and replace the batteries and I removed them alone yesterday and have the bruises to show for it. Suddenly I must put them back for errands today and the weekend. I'll try avoiding injury by using an appliance lever to... lever the metal grid up that needs lifting. Hah! If that works, removing and replacing the batteries will be a piece of cake for ever. Tsk! Really! The Cirrus (aka Easyfold) designers were on drugs to think that chair is foldable in real life.

[Burgerman]

If you really want a folding chair get one of the many chinesium ones as they are all light, alloy, and have small firework lithium batteries like a laptop. But they are actually foldable and very light. Anything with lead either has too small batteries or is too heavy, usually both.

Or.
https://www.sunrisemedical.co.uk/q50-r

Bit heavier but 30 mile range, 30Ah lithium. Easy fold and 30kg or 37kg with battery.

[biscuit]

I don't fold the Cirrus and didn't buy it for its foldability. I think the listing claimed it to be car transportable. Which it is - if the car is a WAV.

The appliance lever worked sort of, I couldn't manage it alone.

That chair has Andersons, 12V and 24V. I struggle to plug them in and out. And they each have a kind of plastic cover. Those covers are no help with plugging. And I have my doubts about the connections under all that plastic. At any rate, the machine has a bad 24V connection now and wrought havoc with my errands today.

What can I do if I haven't the strength to manage those plugs? For a start, do they really need those plastic covers? I would cheerfully cut them off and bin them. Then I could try whether they need less insertion force. Then I would take a look at the pins .

Then I would realise that they are still stiff and now they let in the rain as well??

Maybe some vaseline?

[LROBBINS]

Anderson says that you can put a light coat of oil or grease on the contacts. That does make plugging them in and out easier. You could also lubricate the plastic shells themselves with a dry teflon spray lubricant.

[Burgerman]

I think she means that the normal plastic shells have an additional cover or case on top?
If so bin it...

For what its worth, I use cheap aftermarket andersons, non official for all the solar connections with cables all over the roof, garden, etc in full open weather washed situations a decade ago. No protection, oul or anything else and all working perfectly ever since. Must be around 30 of them in total.

And I used to use the same anderson 50 with off board truck starter spinning the crank in high current direct drive as an external starter on drag race bikes. Thise things pulled 250 upwards amps or more. So I wouldnt worry about a little rain in a power chair!

But if the manufacturer has crimped them, I would worry about that being your high resistance problem. Crimps are problematic.
OR they assembled it badly and a contact/pin isnt located in the shell correctly. So making bad contact.
Yes oil, vaseline etc if it makes it easier to plug in/out. Or a little WD40 if theres some on hand.

That may be your source of low performance.

I don't fold the Cirrus and didn't buy it for its foldability. I think the listing claimed it to be car transportable. Which it is - if the car is a WAV.

When you buy a "folding/portable" chair you are buying two things.
A Flexi/heavier chassis which if you are not planning to fold or lift it is bad.
Smaller battery for weight reasons, again same thing. A problematic compromise for folding. That you dont plan to use.

THIS has a very small footprint. But 55Ah batts, VR2 and has skinny tyres, narrow short base etc. A better compromise. CHEAP new or as new on ebay.
https://www.sunrisemedical.co.uk/q100r

[LROBBINS]

Once in a while I've had a contact slip back in the shell while plugging in resulting in a weak or absent contact. I too use el cheapo fake Andersons, and some of the contact don't have a sharp angle where the spring presses into them so are more likely to slip out of place. A couple strokes with a needle file takes care of that.

[biscuit]

I shall peel the plastic cover off those Andersons, the better to see what I can do.

THIS has a very small footprint. But 55Ah batts, VR2 and has skinny tyres, narrow short base etc. A better compromise

The Easyfold was BNIB at less than the price of a BNIB little indoor chair. I gave the battery little consideration. Or the dimensions, which are like a battleship but that's how wheelchairs are. The only good one I've used indoors where dimensions really matter is my Vienna granny chair and that is because it is shorter than the other indoor chairs.

At the time, I looked very hard at the Q100R at a couple of hundred ££ more used, or a few thousand ££ more BNIB. I like armrests that flip back, non flippable armrests are mega inconvenient (and a little dangerous)* if one is not confined to the chair. So it didn't appeal to me as much as the Easyfold.

*Probably not dangerous unless the driver is as scatty as me.

[Burgerman]

Heres an example of an anderson with a daft cover, and with a contact that is not inserted properly. This one caused trouble!

[biscuit]

Yes, mine are like that.
On Monday I am going to peel the covers off, then I will easify the plugs, then I think I can jemmy the pins out using a screwdriver (iirc from watching YouTube) and see if the connections are sturdy.

[Burgerman]

Scissors.

All those are good for is kkeping the damp in...

Look at the CONTACT in the image. The one on the right is not located correctly. It makes bad connection...

[biscuit]

I think batteries in series normally have the load connected -ve at one end of the series and +ve at the other. My chair has different battery connections - one one of the batteries is not connected to the chair, it's only connected to the other battery. When I tested them separately last week, they were 0.01V different. This imbalance has accumulated since I installed them in about May. Did that wiring cause the imbalance? Is it significant?